What is the recommended treatment for a patient with Iron Deficiency Anemia (IDA)?

Treatment of Iron Deficiency Anemia

Start with oral ferrous sulfate 200 mg (containing 50-100 mg elemental iron) once daily on an empty stomach, and if not tolerated, switch to alternate-day dosing or consider intravenous iron for malabsorption, intolerance, or ongoing blood loss. 1, 2

Initial Oral Iron Therapy

Begin treatment immediately without waiting for diagnostic workup unless colonoscopy is imminent. 1

First-Line Regimen

• Prescribe ferrous sulfate, fumarate, or gluconate at one tablet daily (50-100 mg elemental iron) taken in the fasting state. 1, 2
• Ferrous sulfate 200 mg tablets are the simplest and least expensive option, costing approximately £2.50 for 28 days. 1, 2
• Taking iron on an empty stomach maximizes absorption, though this may increase gastrointestinal side effects. 1

If Oral Iron Is Not Tolerated

• Switch to alternate-day dosing (one tablet every other day), which produces similar hemoglobin increments with significantly lower nausea rates. 1, 2, 3
• Alternate-day dosing avoids the hepcidin surge that occurs 24 hours after iron doses ≥60 mg, which blocks subsequent iron absorption by 35-45%. 1, 3
• Consider ferric maltol 30 mg twice daily as an alternative, which normalizes hemoglobin in 63-66% of patients at 12 weeks, though it is more expensive and slower to replenish stores. 1, 2
• Do not switch between different traditional ferrous salts, as this is not supported by evidence. 1

Monitoring Response to Oral Iron

Check hemoglobin at 2 weeks: absence of at least a 10 g/L rise predicts subsequent treatment failure with 90% sensitivity and 79% specificity. 1, 2

• Recheck hemoglobin every 4 weeks until normalized. 1, 2
• A typical response shows hemoglobin improvement within 1 month of oral therapy. 2
• Continue oral iron for 2-3 months after hemoglobin normalization to replenish bone marrow iron stores. 1, 2
• After restoration of hemoglobin and iron stores, monitor blood count every 6 months initially to detect recurrent IDA. 1

Causes of Treatment Failure

• Non-compliance, malabsorption, systemic disease, bone marrow pathology, hemolysis, continued bleeding, or concurrent vitamin B12/folate deficiency. 1

Intravenous Iron Therapy

Consider parenteral iron when oral iron is contraindicated, ineffective, or not tolerated. 1, 2

Specific Indications for IV Iron

• Intolerance to oral iron despite alternate-day dosing or alternative formulations. 1, 2
• Malabsorption (celiac disease, inflammatory bowel disease, post-bariatric surgery). 2
• Ongoing blood loss that exceeds oral iron replacement capacity. 2
• Inflammatory conditions where oral iron is less effective (active IBD, chronic heart failure, chronic kidney disease). 1, 2

IV Iron Formulations and Dosing

• For patients ≥50 kg: ferric carboxymaltose 750 mg intravenously in two doses separated by at least 7 days, for a total cumulative dose of 1,500 mg per course. 4
• Alternatively, 15 mg/kg body weight up to a maximum of 1,000 mg may be given as a single dose per course in adults. 4
• For patients <50 kg: 15 mg/kg body weight in two doses separated by at least 7 days. 4
• IV iron produces a clinically meaningful hemoglobin response within 1 week. 1, 2
• Monitor serum ferritin levels and keep below 500 mg/L to avoid iron overload toxicity, especially in children and adolescents. 1

IV Iron Administration

• Administer as undiluted slow IV push at approximately 100 mg per minute for doses up to 750 mg, or over 15 minutes for 1,000 mg doses. 4
• May also dilute up to 1,000 mg in no more than 250 mL sterile 0.9% sodium chloride (concentration ≥2 mg iron/mL) and infuse over at least 15 minutes. 4
• Monitor for extravasation, as brown discoloration may be long-lasting; discontinue immediately if extravasation occurs. 4

Repeat IV Iron Treatment

• Check serum phosphate levels in patients requiring repeat courses within 3 months, as hypophosphatemia is a known complication. 4
• Treat hypophosphatemia as medically indicated. 4

Blood Transfusion

Transfusion is rarely required and should be reserved for severe symptomatic anemia with circulatory compromise. 1, 2

• Consider parenteral iron as an alternative before transfusion, as it produces hemoglobin response within 1 week. 1, 2
• If transfusion is necessary, target hemoglobin 70-90 g/L (80-100 g/L in unstable coronary artery disease). 1, 2
• Each unit of packed red cells contains only ~200 mg elemental iron, insufficient to replenish stores in severe IDA. 1, 2
• Iron replacement therapy is still necessary post-transfusion. 1, 2

Special Clinical Situations

Inflammatory Bowel Disease

• Use IV iron as first-line therapy when hemoglobin <10 g/dL, as it has greater efficacy (OR 1.57 for achieving 2.0 g/dL increase) and better tolerability (OR 0.27 for discontinuation) compared to oral iron. 2
• Oral iron may worsen intestinal inflammation and is poorly absorbed in active disease. 2
• Oral iron is appropriate only in mild anemia with clinically inactive disease and demonstrated tolerance. 2

Post-Bariatric Surgery

• Prefer IV iron in severe cases or when oral supplementation is ineffective, as malabsorption is common. 2
• Perform esophagogastroduodenoscopy to exclude anastomotic ulcer disease causing chronic bleeding. 2

Elevated CRP (>4 mg/L)

• Use IV iron as initial therapy when CRP is elevated, particularly if hemoglobin <10 g/dL, as ferritin up to 100 μg/L may still indicate true iron deficiency. 2
• Ferritin is an acute phase reactant and may be falsely elevated in inflammatory states. 2
• Treat the underlying inflammatory condition concurrently, as iron therapy alone will not succeed if active inflammation persists. 2

Chronic Heart Failure

• IV iron improves symptoms, quality of life, and exercise capacity in patients with chronic heart failure and iron deficiency, even without anemia. 2

Chronic Kidney Disease

• Functional iron deficiency is common, and IV iron formulations are specifically approved for this indication. 2

Common Pitfalls to Avoid

• Do not defer iron replacement while awaiting investigations unless colonoscopy is imminent. 1, 2
• Do not interpret ferritin 30-100 μg/L as "adequate" when CRP is elevated. 2
• Do not prescribe modified-release iron preparations, as they are less suitable for prescribing. 1
• Do not give iron doses in the afternoon or evening after a morning dose, as circadian hepcidin increase blocks absorption. 3
• Do not exceed serum ferritin 500 mg/L with IV iron to avoid toxicity. 1